The preparation of chloro-oxy-derivatives of perfluoroalkanes results known from the technical and patent literature: however, the described processes are mostly unsatisfactory, as is better explained hereunder.
Schack and Naya in J.A.C.S. (1969) 2902-91, 11 describe the preparation, by a batch process, at temperatures ranging from -78.degree. C. to room temperature for the first term of the series, CF.sub.3 OCl, whilst, for the higher terms, it operates at -78.degree. C. The operation is carried out with the reactants being in the liquid phase, possibly under their autogenous pressure. It is stated that for the higher terms, the low temperature adopted in the reaction is due to their high unstability at room temperature. As relates to the first term, it would result that even at room temperature, the formation rate is not very high (only 60% after 1 hour).
U.S. Pat. No. 3,842,156 claims gaseous catalysts of the type of SbF.sub.5, HCl, BF.sub.3, which would be preferable to the metal fluorides of the prior art, and would be furthermore suitable for the gas-phase reaction. Actually, the preparation described are carried out at -20.degree. C. on reactants in the liquid state, with very long reaction times (24 hours).
U.S. Pat. No. 3,769,312: in this case too, the process is of batch type, carried out at a low temperature of from -78.degree. to 0.degree. C., preferably -20.degree. C., with reaction times of the order of 10 hours.
Finally, the French Pat. No. 1,589,946 relates exclusively to the synthesis of CF.sub.3 OCl, carried out in the gas phase, at room temperature, batchwise: reaction times of some hours are mentioned. This patent uses catalysts prepared in a special way from MgF.sub.2 and fluorinated Al.sub.2 O.sub.3.
We can conclude hence that from the prior art examined, it results in general that the reaction is carried out in the liquid phase, with very long reaction times. The preferred temperatures are lower than, or at maximum equal to 0.degree. C., preferably -78.degree. C. or -20.degree. C. According to Schack, at room temperature, for the first term, the yield is of 60% only after 1 hour, and for reaching a 99% yield, approximately 12 hours are necessary.
The only process in the gas phase is the one disclosed by the French Pat. No. 1,589,946, limitedly to the synthesis of CF.sub.3 OCl, always by a batch process. In this case too, the times mentioned are very long.